JPH0355801B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the production of a synthetic resin optical transmission body that has a refractive index distribution in which the refractive index gradually decreases or increases in approximately proportion to the square of the distance from the central axis and is not subject to aging. be. It is conventionally known that a transparent body having a refractive index distribution in which the refractive index gradually decreases approximately in proportion to the square of the distance from the central axis acts as a lens. Patent application 1977-106387 (Special application 1977-5857) and
49-88557 (Japanese Unexamined Patent Publication No. 51-16394), a monomer forming a polymer having a refractive index different from that of the reticular polymer is added to a transparent gel of a reticular polymer whose polymerization has not been completed. Polymerization after diffusion from the surface of the object, or polymerization simultaneously with diffusion so that the refractive index changes continuously from the surface toward the inside so that the object has a gradient that gradually decreases from the surface toward the inside. A method for manufacturing a synthetic resin optical transmission body is described. However, all the monomers for network polymers described in Japanese Patent Application No. 106,387/1982 and Patent Application No. 88,557/1987 contain an allyl group (CH ₂ =CH-CH ₂ -). Due to the low polymerizability of the material, about 10% by weight of unreacted allyl groups remain in the optical transmitter, and this gradually polymerizes, causing changes in the refractive index distribution and coloring when left alone. become. The object of the present invention is to provide a synthetic resin optical transmission body that eliminates such conventional drawbacks. In a synthetic resin rod-shaped body that is a refractive index gradient type optical transmitter that has a lens effect, the refractive index of the central axis is
If No, the refractive index N at the distance X from the central axis is expressed by equation (1). Here, A is a positive constant (refractive index distribution constant). N=No(1-1/2AX ² ) (1) A light beam entering from one end of such a rod-shaped synthetic resin body travels while meandering around the central axis. The period L of the meandering optical path is expressed by equation (2). L=2π/√A (2) Let Z be the length of the synthetic resin rod, r the radius, Nr the refractive index around it, f the focal length of this rod lens, and S the distance between the focal point and the end surface of the rod. Tokukai Akira
51-16394, the magnification aberration and image point aberration of this lens are expressed by equations (3) and (4), respectively. △f/f=−△No/No+{1+2πZ/Lcot(2πZ/L
)}△L/L (3) △S/S=-△No/No+{1+4πZ/Lcosec(4πZ/
L)} △L/L (4) Here, △f, △S, △No, △L, and △Nr are respective amounts of change due to changes in λ. Furthermore, the following equation (5) can be obtained from equation (2). △L/L=(△Nr/Nr−△No/No)Nr/2(No−Nr)
(5) As is clear from equations (3) and (4), in order to reduce chromatic aberration, it is necessary to reduce the absolute value of △No/No and at the same time, reduce the absolute value of △L/L as much as possible. is necessary. In the present invention, the monomer Ma forming the network polymer Pa (the refractive index of which is Na) is partially polymerized and gelled to form a rod-shaped or fibrous transparent gel.
A light transmitting body is obtained by diffusing and polymerizing a monomer Mb that forms a polymer Pb (the refractive index of which is Nb) having a smaller refractive index than the transparent gel. Mb
In order to diffuse Mb into the transparent gel, the transparent gel may be immersed in an Mb liquid, or the transparent gel may be placed in an atmosphere containing Mb gas. Inside the optical transmission body, the Pa and Pb components have concentration gradients that gradually decrease and increase, respectively, so as to compensate for each other as they move radially outward from the central axis. Therefore, the refractive index increases radially outward from the central axis. It shows a distribution that decreases continuously toward , and is approximated by equation (1) above. In the ideal case, the central axis consists only of Pa,
The peripheral part consists only of Pb. If △No/No and △L/L in this case are expressed as [△N/N] _e and [△L/L] _e , the following formula (6)
, as shown in (7). [△L/L] _e = {(Nb) _H − (Nb) _C / (N
b) _D − (Na) _H − (Na) _C / (Na) _D } (Nb) _D /2 {(Na
) _D − (Nb) _D }(6) [△N/N _e = (Na) _F − (Na) _C / (Na) _D (7) The subscripts F, C, and D represent the F line, C line, and D, respectively. This is the value for the line. In order to manufacture synthetic resin optical transmitters with small chromatic aberrations and small changes over time, combinations of monomers (including monomer mixtures) must be prepared based on the following conditions.
You can choose Mb. (1) The monomer has high polymerizability, and the amount of unreacted monomer in the synthetic resin light transmitter is preferably 5% by weight or less, more preferably 3% by weight or less. (2) Increase the difference between (Na) _D and (Nb) _D. This difference is preferably 0.030 or more, more preferably 0.040 or more. (3) (Na) _F − (Na) _C / (Na) _D and (Nb) _F − (Nb) _C /
(Nb) Reduce the difference in _D. This difference is preferably 0.0020 or less, more preferably 0.0015 or less. (4) (Na) _F − (Na) _C / (Na) Reduce _D. This value is preferably 0.0090 or less, more preferably 0.0077 or less. (5) Thus, the absolute value of [L _F −L _C /L _D ] _e in equation (13) is of the same order as or less than the absolute value of (Na) _F − (Na) _C / (Na) _D. . The absolute value of this equation (13) is
It is preferably 0.030 or less, more preferably 0.025 or less. In the present invention, as Ma, 2 or more acrylic acid groups, 2 or more methacrylic acid groups, or 1 or more of each
The above condition (1) can be satisfied by using a monomer having at least one acrylic acid group and a methacrylic acid group and no allyl group. Next, examples of monomers (including monomer mixtures) suitable for the present invention that satisfy the conditions (1) to (5) above are listed. As for Ma, (1) Compound represented by R ₁ -R ₂ -R ₃ Both R ₁ and R ₃ are acrylic acid groups or methacrylic acid groups. or,
One of R ₁ and R ₃ is an acrylic acid group, and the other is a methacrylic acid group. _R2 ;

[Formula] (P- or m - isomer) or

[Formula] (P- or m-isomer) (more than 1A group) or −(CH ₂ CH ₂ O) − _n CH ₂ CH ₂ − (m=0 to 20) −(CH ₂ ) _P − (P=3 to 15)

[Formula] (i, j=1-3) or

[Formula] (k =0~20) (more than 1B group) (2) A mixture of the monomers described in (1) above. As Mb (3)

A compound represented by the formula: where X is hydrogen or a methyl group, Y is -(CH ₂ ) _l H (l=1-8) i-propyl, i-butyl, s-butyl, t-
Butyl or (-CH ₂ CH ₂ O) - _p CH ₂ CH ₃ (p-1 to 6) (3A groups) or -(CF ₂ )- _a -F (a=1 to 6) -CH ₂ (CF ₂ ) _b H (b=1 to 8) -CH ₂ CH ₂ O・CH ₂ CF ₃ −(CH ₂ CH ₂ O) _c CF ₂ CF ₂ H (c=1 to 4) −CH ₂ CH ₂ O・CH ₂ (CF ₂ ) _a F (a=1 to 6) −CH ₂ (CF ₂ ) _d O(CF ₂ ) _l F
(d=1~2, l=1~4) or -Si(OC ₂ H ₅ ) ₃ (or more 3B groups) (4)

[Formula] (f = 0 to 2) (5) The mixture of monomers described in paragraphs (4) and (5). Both can be combined, but especially as Ma
If a monomer of the 1B group is used and a monomer of the 3B group or (4) is used as Mb, an optical transmission body with extremely small chromatic aberration and excellent durability can be obtained. Next, examples of the present invention will be described. Example 1 0.1% by weight of benzoyl peroxide (BPO) was dissolved in tetraethylene glycol dimethacrylate (4EDM), filled into a polyethylene casting tube with an inner diameter of 4 mm, and placed in a nitrogen atmosphere.
It was heated to 50.0°C for 68 minutes to form a gel. The obtained cylindrical transparent gel contained 25.0% by weight of reticular polymer (portion insoluble in acetone), trace amount of linear polymer (portion soluble in acetone and insoluble in methanol), approximately 75% by weight.
% by weight of residual monomer (methanol soluble portion). 1,1,3-trihydroperfluoropropyl methacrylate (4FMA) was heated to 50.0° C. under a nitrogen atmosphere, and the transparent gel cylinder was immersed in it for 13 minutes. Then, the cylindrical gel was lifted from the 4FMA liquid layer and heated to 74°C under a nitrogen atmosphere. 1 and a half hours later 80
The temperature was raised to ℃ and heat treated for 20 hours to complete the polymerization. As a result, a hard transparent cylindrical object was obtained. When this material was crushed and extruded with acetone, the extrusion amount was 1.5% by weight. By cutting a transparent cylindrical object to a diameter of 2.03 mm and finishing both ends with flat surfaces perpendicular to the central axis, a rod-shaped convex lens with low chromatic aberration was obtained. A=3.80× ^10-2 mm ^-2 ,
L=32.2 mm, and numerical aperture NA=0.30. A transparent test pattern was closely attached to one end of a rod-shaped lens with a length of 11.3 mm, and the image was observed using F, D, and C lines, and L _F , L _D, and L _C were determined _. L _C /L _D =-0.010, which coincided with the calculated value [ΔL/L] _e =-0.010 of equation (6). This rod-shaped lens was then put to the Sunshine Weather Meter test.
After 500 hours of use, no change in refractive index distribution or coloring was observed. As a comparative example, a gradient index lens was produced in the same manner using diallyl phthalate as Ma, and when a weather meter test was performed for 500 hours, the lens turned yellow. Example 2 A transparent gel of 4EDM was prepared under the conditions of Example 1. The transparent gel was left for 10 minutes in an atmosphere in which nitrogen gas was saturated with vapor of 1.1,3 trifluoroethyl methacrylate (3FMA) at 80.0°C, and then heat-treated at 80.0°C for 20 hours under a nitrogen atmosphere. By cutting the outer periphery, a rod-shaped lens with a diameter of 3.12 mm was obtained. The performance was as follows. A=6.51× ^10-3 mm ^-2 , L=77.9mm, NA=0.19,
L _F −+L _C /L _D = −0.011 ([△L/L] _e = −0.010). Furthermore, when the obtained rod-shaped lens was subjected to a sunshine weather meter test for 500 hours, neither change in refractive index distribution nor coloring was observed. Example 3 0.20% by weight of BPO was dissolved in ethylene dimethacrylate (EDM), filled into a polyethylene casting tube with an inner diameter of 10 mm, and heated to 60.0°C for 50 minutes in a nitrogen atmosphere to gel. . The obtained cylindrical transparent gel contains 14.5% by weight of reticular polymer (portion insoluble in acetone), trace amount of linear polymer (portion soluble in acetone and insoluble in methanol),
It consisted of approximately 85% by weight of residual monomer (methanol soluble portion). 4FMA was heated to 50.0°C under a nitrogen atmosphere, and the transparent gel was immersed in it for 150 minutes. Then, heat treatment was performed under the same conditions as in Example 1. The monomer residual rate of the obtained hard transparent cylindrical object was 2.5% by weight. By cutting the outer periphery, a rod-shaped lens with a diameter of 4.61 mm was obtained. A=5.95× ^10-3 mm ^-2 , L=81.4mm, NA=
0.27, L _F −L _C /L _D =−0.016. [ΔL/L] _e of this system is -0.010. Further, when the obtained rod-shaped lens was subjected to a sunshine weather meter test for 500 hours, neither change in refractive index distribution nor coloring was observed. Example 4 Decamethylene glycol dimethacrylate
0.10% by weight of BPO was dissolved and filled into a polyethylene casting tube with an inner diameter of 4.0 mm, and gelatinized by heating at 60.0°C for 55 minutes in a nitrogen atmosphere.
The obtained transparent gel was incubated at 50.0℃ under nitrogen atmosphere.
After being immersed in 3FMA for 20 minutes, it was heat treated under the same conditions as in Example 1. The outer periphery was shaved to obtain a rod-shaped lens with a diameter of 1.80 mm. A=2.65× ^10-2 mm ^-2 , L=38.6
mm, NA=0.22, L _F −L _C /L _D = −0.013. [ΔL/L] _e of this system is -0.012. Further, when the obtained rod-shaped lens was subjected to a sunshine weather meter test for 500 hours, neither change in refractive index distribution nor coloring was observed. Example 5 0.10% by weight of BPO was added to P-xylenyl dimethacrylate, heated to 80.0°C in a nitrogen atmosphere, melted, quickly poured into the molding tube of Example 1, and heated to 80.0°C for 20 minutes. It was kept and allowed to gel. The reticular polymer content of the obtained transparent gel was 18.7
It was in weight%. This gel was immersed in methyl methacrylate (MMA) heated to 50.0° C. for 100 minutes under a nitrogen atmosphere, and then heat-treated under the same conditions as in Example 1. It's cloudy. By cutting the outer periphery, a rod-shaped lens with a diameter of 1.64 mm was obtained. A=5.41× ^10-3 mm ^-2 , L=85.4mm, NA
= 0.23. Measured by the method described in Example 1
L _F −L _C /L _D =−0.050. And [△L/L] _e was -0.047. Further, when the obtained rod-shaped lens was subjected to a sunshine weather meter test for 500 hours, neither change in refractive index distribution nor coloring was observed. Example 6 0.10% by weight of m-phenylene diacrylate
BPO was dissolved and filled into the molding tube of Example 1, and heated to 60.0° C. for 30 minutes in a nitrogen atmosphere to gel. The resulting transparent cylindrical gel was immersed in MMA under a nitrogen atmosphere and kept at 45.0°C for 80 minutes. Then, heat treatment was performed under the same conditions as in Example 1. The obtained cylindrical solid has a diameter of 0.8 mm from the central axis.
It has the refractive index distribution of formula (1), A=4.53×10 ^-3
mm ⁻² and L=93.4 mm. Some chromatic aberration was observed in the image. Further, when the obtained rod-shaped lens was subjected to a sunshine weather meter test for 500 hours, neither change in refractive index distribution nor coloring was observed.

Claims (1)

[Claims] 1 Monomer (including monomer mixture) Ma that forms network polymer (including copolymer) Pa (its refractive index is Na) is partially polymerized and gelled to form a transparent solid object, and Na A monomer (including a monomer mixture) Mb forming a polymer (including a copolymer) Pb having a refractive index different from that of Nb is diffused into the transparent solid object and polymerized, so that the refractive index is different from that of the surface. In the method for manufacturing a synthetic resin light transmitting body that continuously changes from the inside toward the inside, Ma is 2 or more acrylic acid groups, 2 or more methacrylic acid groups, or 1 or more acrylic acid groups and methacrylic acid groups. A method for producing a synthetic resin optical transmitter with excellent durability, characterized by using a monomer having an acid group and no allyl group.